Hydraulic pump and control valve assembly



April 4, 1961 w. T. LlvERMoRE 2,977,883

HYDRAULIC PUMP AND CONTROL vALvE ASSEMBLY Filed Feb. 24, 1955 4 sheets-sheet 1 April 4, 1961 w 1 LNERMORE 2,977,888

HYDRAULIC PUMP AND CONTROL VALVE ASSEMBLY Filed Feb. 24, 1955 4 sheets-sheet 2 Y INVENToR.

W/ /M 7T VER/V1 OPE ATTORNEYS www@ April 4, 1961 w. T. LNERMQRE 2,977,888

HYDRAULIC PUMP AND CONTROL VALVE ASSEMBLY Filed Feb. 24, 1955 4 Sheets-Sheet 3 e/ e l 74 62 6a 69 ea J7 74 IN VEN TOR.

w/UAM 7: f1/IPM ok- April 4, 1961 w.1. LlvERMoRE 2,977,888

HYDRAULIC PUMP AND CONTROL vALvE ASSEMBLY Filed Feb. 24, 1955 A 4 sheets-sheet 4 le- E Zag/725%@ HYDRAULIC PUMP AND CONTROL VALVE ASSEMBLY William T. Livermore, Grosse Pointe-Farms, Mich. (509 Middle River Drive, Fort Lauderdale, Fla.)`

FileeFeb. 24,l 195s, ser. No. @11,238`

z3 Claims. (el. 10s-42) This invention relates to a pump and valve assembly particularly adapted for use in a recirculating hydraulic pressure system involving intermittent, varying and high pressure requirements.

.One applic-ation for which the device is-`particularly suited is that of a power steering system wherein, in 2 ple, while turning the Wheels of a stationary vehicle` in heavy mud, maximum pressures in the order of v75() psi. maybe required,V and substantial pressures may likewise be involved in ordinary parking-maneuvers when wheel turning is not facilitated by vehicle movement.` Verylmuch lower pressures are involved inrnormal steering operations withthejvehicle underway and during periods of straight-away driving Very little, if any power may be called for.

Under these circumstances, the most severe requirements on the pumping system are normallyencountered when the vehicle isstationary with the engine running at idling or slightly over idling speed, Vwhile minimum power requirements are involved'when the vehicle and engine are running at high speed. Since a pump for such system is normally driven through suitable fixed ratio gearing from the engine, such as by a direct coupling to an extended generator shaft which may rotate at a speed in the order of 1.8 times engine speed, the pump must have sucient volume and pressure characteristics to meet the most severe requirements encountered with the engine running at or close to idling speed. Accordingly, in the case of any ixed displacement pump, a relatively large volume of oil will pass through the pump at the` high engine speeds when the pressure requirements are relatively low. If the entire output of the pump were at all times continuously circula-ted through the hydraulic steering gear excessive ilow would be involved and large passages required; and, if the pumping pressure head were constantly maintained at the maximum value, an excessive amount of work would be required accompanied by undue heating of the oil and high power losses.

Accordingly, it has been found desirable in such systems to provide means for by-passing a major portion of they pump output at high speed directly tothe pump inlet without passing through the hydraulic steering-gear i thereby greatly reducingY the tlow through the steering system, Vand also to provide means for maintaining a relatively low normal pressure head increased only as required to meet power steering demands in order to minimize work loss and heating'inthe pumping system. Various. forms. of more or less complicated flow con- 2,977,888 estantes Aps. a, reet trol valves have been developed in the past to eiect such by-passing of the discharge of the pump whenever the output volume exceeds the immediate power requirements and; whenever the pressure ofthe output exceeds a maximum safe value.

The present invention is directedprimarily to simplifying and reducing the cost of the valve and pump construction for meeting these requirements. In this connection, the adaptation of a loose slipper pump yof the general type disclosed in my United States Patent No. 2,599,927 to the requirements of hydraulic steering pumps has been undertaken with a View to substantially reducingrcosts of manufacture in this held. While the initial units designed andtested for this purpose gaver early promiseiof meeting Volume and pressure requirements encountered in actual vehicle operations, a number of rigorous bench tests Vimposed by vehicle manu- -f actur'ers to'V uncover deficiencies under the most extremeV operating conditions disclosed the necessity of many important and several critical structural modications which ,were not apparent upon initial analysis, design and testing. For example, `accelerated wear endurance tests such as 24 h our operation at 10,000 r.p.rn. were found to produce wear points in the housing and slippers, slipper breakage, and slipper spring failure. hand, high pressure tests devised to by-pass all of the discharge under maximum pressure directly back to the inlet at the-pump for prolonged periods of time were found to increase the oil temperature to a point where expanding portions of the pump would cause binding. Various modifications devised to provide satisfactory op-q eration under such rigorous test conditions have proved s of great importancein achieving maximum capacity,

durabilityand quiet operation under the Wide range of operating conditions demanded for thecommercially ac.

ceptable power steering pump of this type. More specically, itis an object of the present invention to provide a single spring loaded valve which is adapted to perform all of the necessary pressure regulating and by-passing functions incident to the use of a fixed displacement rotary pump in a system of the type described.

Another object is to adapt such valve to circulate a relatively small volume of low pressure. oil through the power circuit when there is no power demand, or when any power demand is satisfied, in order to keep the power circuit iilled with oil at all times.

Another object is to adapt such valve to. open to the by-pass position, to inject directly into the intake of the pump any output exceeding thev requirements for the above-mentioned circulation through the hydraulic circuit either under the condition of no power or power demand.

Another object is to adapt such valve to block automatically any by-pass flow to the inlet of the pump during any demand for power until such demand is satised.

ing the by-pass fluid tangentially into the inlet portl to effect a Velocity injection lling of such port.

Another object is to develop a pressure head for producing such velocity injection lling of the inlet port adequate to overcome any centrifugal oil pressuresA tend-v ing to produce cavitation. Y

Another object is to employ a restricted orice flow On the otherA from the discharge port of the pump to the power circuit and to employ the pressure head built up against such orifice for moving said valve to a by-pass position.

Another object is to employ a spring to oppose such movement of the valve in order to establish Ia. minimum flow through the power circuit.

Another object is to make such spring of sufiicient strength to establish a pressure head exceeding atmospheric pressure by a sufficient value to assure adequate velocity injection filling to the inlet port'to avoid cavitation.

Another object is to employ pressure resistance in the power circuit to supplement such spring in opposin movement of said valve to a by-pass position.

Another object is to employ a small differential area between the effective area of such valve upon which said pressure in the power circuit acts and the area of the 'valve upon which the pump discharge pressure acts tending to open the valve to by-pass position such that the discharge pressure of the pump will overcome both the spring and the supplementing pressure in the power circuit after such power circuit pressure exceeds the maximum pressure for which the system is designed thereby causing such valve to operate as an automatic safety unloading valve.

Another object is to adapt such differential area to cooperate with the differential pressure across said orifice to cause said valve to by-pass any excess dischargeof the pump even when the pressure requirements of the power system are at an intermediate or relatively high value short of maximum pressure.

Another object is to prevent any pumping action arising from movement of the valve due to changes in volume between the differential areas of the valve from interfering with smooth intake from reservoir to the inlet port of the pump.

Another object is to adapt a loose slipper type of rotary pump such as disclosed in my prior United States Patent No. 2,599,927 to the requirements of a high press ure, high speed power steering circuit. v

Another object .is to provide a slipper construction for such pump adapted to operate quietly at high speeds without cavitation.

Another object is to provide a slipper spring which will oppose slipper advancing in its notch.

Another object is to provide means for preventing slipper spring buckling.

Another object is to control slipper clearance in a manner such as to positively prevent excessive slipper shifting in its notch.

Another object is to provide a slipper construction of high strength and wearing properties which may be economically produced.

Another object is to provide means for conducting bearing leakage oil to the main supply sump in order to introduce cool oil into the pump even when full discharge is directly by-passed to the pump inlet.

Another object is to provide means for minimizing pump noise under all conditions of operation.

Another object is to provide means for assembling the pump which will automatically compensate for dimensional variations in the size and location of the respective parts.

These and other objects will be more apparent from the following detailed description of a preferred embodiment of my invention and from an examination of the drawings disclosing such embodiment wherein:

Fig. l is a sectional side elevation of the pump and valve assembly shown in relationship to an oil reservoir and connecting pressure outlet and return lines, such sectional view being taken transversely of the pump rotor and longitudinally of the valve bore.

Fig. 2 is a sectional elevation taken along the line 2-2 of Fig. 1, showing a transverse section of the valve and longitudinalsection of Athe pump rotor. q

Fig. 3 is a sectional elevation taken along the line 3--3 of Fig. l showing the form of the inlet port.

Fig. 4 is a sectional elevation taken along the line 4-4 of Fig. 1 showing the form of the outlet port.

Fig. 5 is a sectional elevation of the right end of the valve taken along the line 5-5 of Fig. 1.

Fig. 6 is an enlarged fragmentary view of the pump rotor shown in Fig. 1 with the valve displaced to a bypass position.

Fig. 7 is an enlarged view of one of the pump slippers taken along the line 7--7 of Fig. 6.

Fig. 8 is an enlarged sectional view of one end of a slipper taken along the line 8-8 of Fig. 7.

Fig. 9 is a modified valve construction similar to that shown in Fig. l.

Fig. l0 is a further modified valve construction similar to that shown in Fig. l.

Referring to Figs. l and 2 it will be seen that the pump and valve assembly comprise a main center housing A for valve and pump rotor, a front housing B for a rotor shaft bearing and drive coupling, a rear housing C for a second rotor shaft bearing, a pump rotor D, and a spool valve E. The main body A is provided with a transverse bore 10 in which the cylindrical pump rotor D operates and a longitudinal cylindrical bore 11 in which the spool valve E may move in an axial direction. Needle bearings 12 run in a closed end bearing race 13 pressed into a cylindrical bore 14 in the rear housing C and rotatably support a bearing shaft extension 15 of the pump rotor while similar needle bearings 16 rotatably'support a rotor drive shaft extension 17 in the front housing B which may be coupled with a suitable source of power such as an extension of a generator shaft, not shown.

The center housing A is assembled to the front and rear housings B and C by four bolts 1S while a pair of dowel pins 19 accurately locate the respective housings in correct alignment. Flat machined surfaces of the respective housings register directly against each other in assembled position with circular 0 rings 20 seated in annular grooves in the respective rear and forward housings providing a seal against oil leakage between adjacent surfaces.

The travel of the valve E in the bore 11 is limited in one direction by a valve plug 21 which is held against outward displacement by a lock pin 22 and includes an 0 ring oil seal -23, while at the other end valve travel is limited by the inner end of an outlet fitting 24 screwed into an enlarged end of the bore 11 and into oil sealing engagement with a metal washer 25. A spring 26 is seated in the outlet fitting 24 and a recessed end of the valve E urging the valve toward engagement with the valve plug 21.

An oil reservoir 27 located above the valve and pump assembly communicates with a pump inlet port 28 centrally disposed at one side of the pump bore 10 through an inlet fitting 29 and passage 30 intersecting the valve bore 11 above an intersection 31 of the inlet port 28 with such valve bore. A necked portion 32 of the valve E between annular lands 33 and 34 provides constant communication between the oil reservoir 27 and inlet port 28 throughout the extremities of travel of the valve between the end plug 21 and outlet fitting 24.

The pump rotor D is provided with a plurality of (preferably four) rectangular notches 35 which extend across the entire length of the rotor between the housings B and C. Within each of such notches a loosely mounted slipper 36 extends throughout the length of the rotor and is urged radially outwardly by a pair of compression springs 37 located near the ends of the slipper and seated in recesses formed in the rotor and slipper, respectively, as best shown in Fig. 2. The rotor length is equal to the width of the center housing less working clearance between the rear and front housing faces and the slippers are preferably, constructed with a length providing slight additional working clearance relative thereto.

An outlet port 38 communicates centrally witlithe s-ide of the rotor bore opposite that of the inlet port 28 and with the valve bore 11'as best shown in Fig. 1. As the'rotor turns in a counterclockwise direction as seen in Fig. l, each slipper moves through an inlet arc of increasing radius, a Working arc of constant radius, an outlet arc of decreasing radius, and a sealing arc of constant radius, thereby pumping a volume of oil between inlet and outlet ports proportional to the speed of rotation. From the outlet port 38, oil passes through a transverse orifice 39 in the necked portion of the valve E between annular lands 34 and 40, through a central passage 41 in the valve, `an outlet passage 42 in the tting 24, through a hose connection 43 to the power steering gear, not shown, and therefrom through return line 44 to the reservoir.

Oil pressure in the outlet port 38 also communicates with the right end 45 Vof the valve E through a fiat 46 on one side of theland'40 and when the volume of flow through the orice 39 is great enough to createra pressure differential between the right and left ends of the valve sufficient to overcome spring 26, the valve will shift to the left moving land 34 across the right margin of the inlet passage 31, by-passing fluid fromthe outlet port directly to the inlet port. As long as the flow through the steering gear is relatively unrestricted, as where no power is demanded, the valve E will provide a relatively low pressure by-pass. However, upon a steering demand arising which blocks the unrestricted flow through the steering gear, a drop in pressure differential across the orifice 39 will permit the pressure of spring 26 to return the vvalve to the position shown in Fig. 1 blocking the by-pass flow and thereby directing the full output of the pump to meet any power requirement within the pressure capacity of the system.

In order to provide a safety limit to the maximum pressure of the system, the left-hand land 48 of the valve E and bore 11a are constructed with a slightly smaller diameter than the remaining valve lands and bore 11b such that when the pressure reaches a predetermined maximum value, the outlet pressure on the larger right end of the valve will overcome the spring 26 even in the absence of flow through the power system and with no pressure drop across the orifice 39.

A land 49 is provided between the smaller diameter land 48 and the inlet passage 30, and an auxiliary vent 50 is provided between the reservoir 27 and the valve bore between the differential lands 48 and 49 in order to prevent any interruption or interference with smooth i flow from the reservoir to the inlet port 28 as la result of displacement offluid between the differential lands upon any rapid movement of the valve toward the left.

While the construction and general operation of the pump and valve assembly willnbe understood from the above description, there are a number of important factors in adapting the present construction to the high speed, high pressure requirements of an automotive power steering system which require a more detailed explanation.

. In the case of a direct drive from the generator shaft of an automotive vehicle, speeds in the order of 1.8 times crank shaft speed may be involved so that in order to provide an Vadequate safety factor the pump must be constructed to operate efficiently and quietly at speeds in the order of ten thousand r.p.m. On the other hand, maximum pressure demands at or near engine idling speed may be in the order of 750 p.s.i.

In order to minimize centrifugal effects on the oil and slipper elements arising from high speed operation, it has been found important to employ a rotor of small diameter proportioned to produce necessary volume requirements by Yemploying a length of rotor at least equal to and preferably in excess of itsv diameter.

Even with the use of a small rotor, for example, in the order of 11A inches in diameter, the centrifugal effects on the oilin the slipper cavity; during the filling cycle of slipper -travel'through'the intake` arcfare Such asv to require special provisions to `avoid cavitation and-noisy operation resulting therefrom when the pump is running at high speeds. Since such centrifugal effects on the oil column between the base of the slipper' notch and spring cavity and the intake port will exceed atmospheric pressure, feed from the reservoir alone cannot be relied upon even though the reservoir is placed above the pump as shown in Fig. l. In practice it has been found essential to supplement such reservoir feed with velocity injection from the by-,pass operation of the valve as shown in Fig. 6, such velocity 'injection' feed being under a sufficient pressure head to at least compensate for any excess of centrifugal force over atmospheric pressure. Accordingly, in practice, it has been found desirable to load the valve E with a spring 26 of sufficient strength relative to the differential area of the valve and size of the orifice 39 to develop a minimum pressure head in the order of 4f).p.s.i. in the outlet port before the valve opens to bypass. By constructing the intersection 31 of the inlet port 28 with the valve bore 11 over a limited arc at the bottom of the bore, for example, with a total intersection arc of 90, all of the oil by-passed by movement of the valve land 34 over the inlet port will be directed downwardly toward the bottom of the inlet port in a direction -tangential to slipper travel, the velocity of such fluid assisting simultaneous How from the reservoir and having no component in any way obstructing ow from the reservoir. Since the by-pass oil is delivered under a tangential velocity in the direction of slipper travel, it becomes correspondingly unnecessary for the sl-ipper to accelerate the oil in the inlet port and as the velocity` head of such fluid is transformed to pressure at the bottom of the inlet port, such pressure becomes adequate to overcome any centrifugal effects on the oil in the slipper cavity and to force complete filling of such cavity.

In order to facilitate such complete filling and minimize the noise of pump operation, each slipper is constructed intermediate the end spring seats with a recess defined by beveled surface 55, as shown in Fig. l, which extends across substantially the entire inlet port 28, best shown in Fig. 3, in order to provide a relatively unrestricted opening for oil flow from the inlet port to the notched chamber under the slipper and to form a scoop to assist in filling such chamber under the slipper.

High rotor speeds and resultant centrifugal forces on the slippers as well as high maximum pumping pressure requirements impose critical limitations on the contour of the bore 10 in which the rotor operates and the related slipper face 60 which engages such bore. With reference to Fig. 6, one form of bore which has proved satisfactory in operation employs a sealing arc of .625 inch radius extending 22 on either side of the vertical center of .562 inch radius tangential'to the working arc 57, arcs 61 and 62 being tangential to each other. The rotor preferably has a radius equal to the sealing radius ofthe bore less Working clearance. Satisfactory working engagement in a bore formed of the aforementioned arcs has been found to obtain by providing the face 60 of the slipper with a central radial arc 63 equal to the radius of the working arc 57 together with tangential radial arcs 64 equal to the mini-mum radial arc 62 of the bore, the corners 65 being broken with a %4 inch radius. With such related'slipper and bore dimensions it will be seen that the slipper face will provide a substantial area contact with the borre throughout the working arc where the slipper alone is depended upon for sealing area contact and will also provide substantial edge area c-ontacts with that portion of the bore 62 having the most severe curvature and therefore. highest acceleration loads on the slipper. The slipper will engage the sealing arc of the bore with line contacts at the points of tangency between the respective arcs onthe slipper face during which period sealing requirements of the slipper are at a minimum due to the effectivel seal between the rotor and the bore, while the slipper face will engage the arc 61 with a single line contact where acceleration loads due to curvature are at a minimum. The cut-off edge 66 of the outlet port is located so as to be passed by the leading sealing edge of the slipper after the slipperhas reached substantially its innermost position in the sealing arc `so that no change in volume in the cavity under the slipper will take place after such passage. The cut-off edge 68 of the inlet port is likewise positioned for passage by the sealing surface 63 of the slipper after the slipper has reached its outermost position in the working arc. The working arc of the bore between the cut-off point 68 of the inlet portY and the opening point 69 of the outlet port is sufficient to assure full registration of the sealing arc 63 of at least one slipper between such points at all times. However, in order to minimize noise believed to arise from air shock in opening to pressure incident to slight air inclusions in the oil, a progressive V groove 70, best shown in Figs. 4 and 6, is provided which extends back to a point 71 just short of direct port-to-port connection between adjacent sealing slippers when at the position shown in phantom, thus providing a gradual build-up of pressure on the column of fluid between such adjacent slippers in the working arc when the leading slipper uncovers outlet pressure.

While frictional forces normally tend to hold the slippers back against the rear driving surface of the notch and centrifugal forces normally tend to urge the slippers outwardly into proper engagement .with the bore in the rotor housing, certain forces may create a tendency for the slippers to shift forwardly in their notches, for example, at that portion of their travel through the inlet port where a component of the centrifugal force urges the slipper forward or at the end of the travel in the outlet port where a reduction in the radial position increases the angular speed of the slipper, or through the sealing arc where pressure leakage may induce forward shifting leading to objectionable noise in operation. In order to more positively urge the slippers backwardly into engagement with the rear driving surface of the notch, inclined compression springs 72 are employed between the rotor and either slipper end as best shown in Fig. 6, appropriate seats 73 and 74 being provided in the respective rotor and slippers to provide such inclination. In order to prevent such compression springs from buckling, stabilizing pins 75 having a length just short of minimum spring length are provided.

In order to further provide against the possibility of any noise effect from slipper shifting, the base of the slipper is'formed with a clearance in the order of .009 inch relative to the width of the rotor notch while the radially outwardly extending forward and rear faces of the slippers are sufficiently relieved to permit the necessary rocking action of the slipper withinthe notch in following the contour of the pump bore, all as clearly shown by the various positions of the slippers in Fig. 6. Thus, even if at extremely high speed operation, acceleration forces overcome the effective springs 72 in holding the slippers back against the driving surface of the notch, any possible forward movement of the slipper in its notch will be so slight as to render any resulting'noise effec-t inaudible.

Slippers formed of sintered powdered steel induction hardened running against a suitably hardened bore surface of a hardenable cast iron housing has been found to provide very satisfactory running properties under the rnost severe endurance tests to which the pump has been subjected.

In order to provide adequate cooling for the oil in endurance tests where full discharge of the pump is directly by-passed to the intake under maximum pressure for protracted periods of time, it has been found desirable to return bearing leakage oil to the sump by separate passage not directly associated with the pump intake from the oil reservoir, in order that bearing leakage oil maybe replenished from the relatively cool oil in the reservoir. Referring to Fig. 2, it will be seen that suitable oil passa-ges 76, 77 conduct oil from the needle bearings 12 in the rear housing C to a passage 52 in the front housing B which also communicates with the front needle bearing 16 and conducts oil therefrom to a passage 53 in the center housing A leading to the oil reservoir, an O ring seal 54 being provided at the inner face juncture of the vent passages 52 and 53. Such venting of oil leakage through the needle bearings also prevents pressure from building up on the packing 51 thereby preventing leakage to the exterior of the pump.

In a high pressure pump such as the present where the rotor is required to run with minimum sealing clearance relative to one side yof the bore which requires very accurate positioning of the rotor in the bore, a serious manufacturing and assembly problem arises due to cumulative tolerances in the size and location of the journal bearings, rotor bore, journals, etc.v In order to avoid impractical narrow ranges of tolerances, unduly expensive selective assembly procedures or similar relatively expensive conventional procedures for maintaining uniform and accur-ate positioning of the rotor in the housing bore, it has been found highly desirable in the present case to complete the drilling of one of the dowel holes 19 after preliminary assembly of the pump, and during temporary clamping of the respective housings. Thus with one of the dowels acting as a pivot for the respective housings A, B and C, and with the rotor journals assembled in their respective bearings and the faces of the respective housings in contact, the position of the end housings B and Cv may be shifted relative to the center housing A until a proper location is established between the rotor or a gauge plug simulating the rotor, and the bore in the central 4housing A whereupon the respective housings are suitably clamped While the other dowel hole is finish drilled thereby assuring desired take-up of clearances and automatic compensation for all tolerances in the respective size and location of the elements contributing to the relative positioning of rotor and bore surfaces. Referring to Fig. 9, a modified valve construction is shown generally similar to that of Fig. l with respect to its function of by-passing fluid from the outlet port to the inlet port but having certain different control characteristics. Thus, instead of employing a differential area as in the case of the valve of Fig. l, a valve bore 80 of uniform dimension throughout is employed along with a cylindrical valve 81 which includes a press fit bushing 82 having small plunger 82a urged by spring 83 acting on a headed pin 83a to block flow from chamber 85 into a cross passage 84 whenever delivery pressures in chamber S5 are below themaximum safety release pressure. A drilled passage 86 in the valve housing conducts fluid from the outlet port 38 through a restricted orifice 87 to the discharge passage thereby developing a pressure differential acting on the respective ends of the valve 81 increasing with flow, as in the case of the valve of Fig. l where such pressure differential was built up across orifice 39 conducting output fluid through the center of the valve. The differential pressure across the orifice 87 accordingly will operate to move the valve 81 to the left against the resistance of the spring 26 when the pressure differential across such orice reaches a predetermined value such as 40 p.s.i. thereby controlling the flow t-o the discharge chamber 85 and passage 42. When flow through the outlet passage 42 is completely blocked and pressure in chamber 85 builds up to a safety release pressure, plunger 82a is moved to the right against spring 83 permitting discharge of outlet pressure through cross passage 84 to the inlet port 28 and the resultant flow across orifice 87 again moves the valve to the left for direct discharge from outlet to inlet port. The plunger 82a, which may be asimple cylindrical needle bearing,

is preferably constructedh with one or more narrow ilats 8-9 which conduct atmospheric pressure from the' cross passage 84 to the'spring chamber 90 permitting the'pressure of spring 83 alone to'V control theiultimatesafety re"- lease pressure at which the valve will unload. The flats 89 are preferably of small area providing restricted orilice dashpot effect for the oil in the chamber 90 iny order to eliminate any hunting tendency for the plunger 82a.

It will be understood that since the plunger 82a' remains closed at pressures below the maximum safety release pressure, the pump is capable of delivering'iluid at high pressures'to the youtlet line 42 at the same'rate of flow as at lowpressures'dueto the absence of'differential areas of the valve' operating with increasing pressure to increasingly oppose the bias of spring 26' as in the case of the valve of Fig. l. The practical effect of thisA is to' permit an equally fast turning rat'e'n` the power steering mechanism when maximum resistance to wheel turning is encountered as well as ini the case of very low resistance. i

Referring to Fig. 10, a further modified valve is shown similar in all functional respects to that of Fig'. 9 ,except that a ball checklvalve 91 is employed in place of the plunger 82a to control the safety release pressure.

While a particularembodiment of the complete pump and valve -assembly and certain modified valve constructions, all of which have provedV highly satisfactory in operation, have been described in detail, it is to be understood that numerous changes" in detailed construction might be resorted to without departing from the scope of my invention as defined in the following claims.

I claim: v

l. A pump comprising a pump housing, a rotor bore in said housing, substantially parallel oppositely' directed inlet and outlet ports in said housing" communicating tangentiallywith opposite sides of said bore, said ports being substantially centrally disposed relative t-o the length of said bore, a valve bore in said housing extending transversely of said rotor bore and intersecting said respective inlet and outlet ports, the transverse dimension of said valve boi-e (taken parallel to the axis of said rotor bore) being at least as great as the corresponding dimension of said intersecting inlet port, a uid reservoir communicating with said inlet port, a rotor eccentrically mounted in said'rotor bore carrying free slippers adapted to produce a positive displacement fluid' pumping action between said inlet and outlet ports, and a valve movable to open or shut off direct communication between said outlet and inlet ports .through said valve bore, sai-d inlet port, valve bore and valve being adapted and arranged to inject output fluid under pressure from said valve bore directly into said inlet port substantially tangentially of said rotor in the direction of slipper travel through said inlet port when said valve is moved to its open position thereby to assist in overcoming high speed centrifugal forces tending to oppose co-mplete filling of said pump.

2. A pump comprising a pump housing, a'rotor bore in said housing, substantially parallel oppositely directed inlet and outletl ports' in saidV housing communicating tangentially with opposite sides of said bore, said ports being centrally Vdisposed relative to the length of said bore, a valve bore in said housing extending transversely of said rotor bore and intersecting said respective inlet and outlet ports, the transverse dimension of said valve bore (taken parallel 4to the axis of said rotor bore) being at least as great as the corresponding dimension of said intersecting inlet port, la fluid reservoir communicating with said inlet port, a rotor eccentrically mounted in said rotor bore carrying free slippers adapted to produce a positive displacement uid pumping action between said inlet and outlet ports, a spool valve axially movable to openr or shut olf direct communication between said outlet and inlet ports through said valve bore, said valve having an annular land adaptedto uncover a portion of said inlet port ink said open position, said- 'inlet port in'ters secting said valve bore over a limited farc such as to cause a conlined stream of output uid under pressure to be injected from said valve bore directly into saidy inlet port substantially'tangent to said rotor in the direction of slipper travel through said inlet port when said valve land is moved to uncover said' inlet port.

3. A pump comprising a pump housing, aV rotor bore in said housing, substantially parallel oppositely directed inlet and outlet ports in said housing communicating-with opposite sides of said bore, a valve bore in said housing extending transversely of said rotor bore and intersecting said respective inlet and outlet ports, the transversedimension' of said valve bore (taken paralleli to the axis of said rotor bore) being at least as great as theV corresponding dimension of said intersecting inlet port, rotary pump means disposed in said rotor bore adapted toproduce positive displacement pumping action between said inletand outlet ports, and a valve movable to open or shut oft direct communication between said outlet and inlet ports through said valve bore, said valve and'valve bore including means directing the flow of bypassed iluid substantially tangential to and in the direction of rotation of said rotary pump means.

4. A pu-mp comprising a pump housing, a rotor bore in said housing, substantially parallel oppositely directed inlet and outlet ports in said housing communicatingA with opposite sides of said bore, a valve bore in said housing having an -axis intersecting said respective inlet and outlet ports along a line substantially normal thereto, the transverse dimension of said valve bore (taken parallel to the axis of said rotor bore) being at least as great as the corresponding dimension of said intersecting inlet port, a fluid reservoir communicating with said inlet port, fluid discharge passage means including an orifice cornmunicating with said outlet porti. rotary pump means disposed in said rotor bore adapted to produce positive displacement pumping action between said inlet and outlet ports, a valve movable to open or close off direct communication between said outlet and inlet ports through said valve bore. spring means biasing said valve to closed position and the pressure differential across said orifice responsive to increasing ilow rate through said discharge passage urging said valve to Said open position.

5. A pump asset forth in claim 4 including means responsive to increasing output pressure for moving said valve to said open position. i

6. A pump as set forth in claim 4 including means responsive to'in'crea'sing output pressure for moving said valve to said open position, said last means beingfad-apted in the absence'of ow through said discharge passage to overcome said biasing means at a maximum safety release pressure.

7. A pump as set forth in claim 4 wherein said Valve is provided with differential areas oppositely subjected to iluid pressure adapted to overcome said biasing means at a maximum safetv release pressure in the absence of flow through said discharge passage.

8. A pump comprising a pump housing. a rotor bore in said housing, substantially parallel oppositely directed inlet and outlet ports in said housing communicating with opposite sides of said bore, al Valve bore in said housing extending transversely of said rotor bore and intersecting said respective inlet andoutlet ports, a fluid reservoir communicating with said inlet port, a uid discharge passage communicating with said outlet port, .rotary pump means disposed' in said rotor bore adapted to produce positive displacement pumping action between said inlet land outlet ports, a spool valve axially movable in said valve bore to open or'close ol direct communication between said outlet and inlet ports through said valve bore, a spring biasing said valve to close off said communication, orifice means interposed between said outlet port and said discharge passage'creating a pressure differential increasing with flow, opposed areas of said valve being subjected -to said pressure differential in a direction opposing said spring bias.

9. A pump as set forth in claim 8 wherein said opposed areas are unequal so as to create additional force opposing said spring, said latter force being suflicient in itself in the absence of pressure differential arising from flow to overcome said spring and open said valve at apredetermined maximum safety release pressure.

10. A pump as set forth in claim 8 wherein an auxiliary passage is provided between said discharge passage and said pump inlet, and wherein safety release valve means are provided to normally block said auxiliary passage and to open said passage when a predetermined safety release pressure is established in said discharge passage.

11. A pump as set forth in claim 8 wherein an auxiliary passage is provided between said discharge passage and said pump inlet, and wherein safety release valve means are provided to normally block s-aid auxiliary passage and to open said passage when a predetermined safety release pressure is established in said discharge passage, said safety release valve means comprising a spring loaded cylindrical plunger normally blocking said auxiliary passage, an end area of said plunger being subjected to pressure in said discharge passage.

l2. A pump as set forth in claim 8 wherein an auxiliary passage is provided between said discharge passage and said pump inlet, and wherein safety release valve means are provided to normally block sai-d auxiliary passage and to open said passage when a predetermined safety release pressure is established in said discharge passage, said safety release valve means comprises a spring loaded ball valve normally blocking flow from said discharge passage through said auxiliary passage.

13. A pump as set forth in claim S wherein an auxiliary passage is provided between said discharge passage and said pump inlet, and wherein safety release valve means are provided to normally block said auxiliary passage and to open said passage when a predetermined safety release pressure is established in said discharge passage, said safety release valve means comprising a spring loaded cylindrical plunger normally blocking said auxiliary passage, an end area of said plunger being subjected to pressure in said discharge passage and the other end of said lplunger extending into a chamber in which oil is trapped to act as a dashpot to dampen any hunting tendency of said plunger.

14. A pump as set forth in claim 8 wherein an auxiliary passage is provided between said discharge passage and said pump inlet, and wherein safety release valve means are provided to normally block said auxiliary passage and to open said passage when a predetermined safety release pressure is established in said Vdischarge passage, said safety release valve means comprising a spring loaded cylindrical plunger normally blocking said auxiliary passage, an end area of said plunger being subjected to pressure in said discharge passage and the other end of said plunger extending into a chamber in which oil is trapped to act as a dashpot to dampen any hunting tendency of said plunger, and a restrictive passage connecting said chamber with the pump inlet thereby to control the degree of dampening action. i

15, A pump comprising a pump housing, substantially parallel oppositely directed inlet and outlet ports communicating with said housing, fluid pumping means for moving fluid from said inlet port to said outlet port, a valve port communicating with said outlet port, a reservoir and connecting passage therefrom to said inlet port for supplying fluid thereto, said inlet port intersecting said valve bore, the transverse dimension of said valve bore (taken parallel to the axis of said rotor bore) being at least as great as the corresponding dimension of said interesting inlet port, a spool valve in said bore having an annular sealing land adapted to block communication between said outlet and inlet ports, said land being movable to open communication from said outlet port to said inlet port, said inlet port intersecting a limited arc of said valve bore facing in substantially the same direction as inlet flow from said connecting passage whereby movement of said annular land to uncover said intersection will result in directed injection of fluid under pressure from said outlet port into said inlet port, said connecting passage communicating with said valve bore and said inlet port on the low pressure side of said sealing land.

16. A pump comprising a pump housing, substantially parallel oppositely directed inlet and outlet ports communicating with said housing, fluid pumping means for moving fluid from said inlet port to said outletport, a discharge passage communicating with saidroutlet port, a valve bore communicating with said inlet and outlet ports, a cylindrical spool valve having a sealing land axially movable to positions for opening or blocking said communication through said valve bore, an orifice interposed between said outlet port and said discharge passage for establishing a pressure differential therebetween increasing with flow through said discharge passage, means biasing said valve to close communication between said outlet and inlet ports, means responsive to said differential pressure urging said valve to open said communication, a limited arc of intersection between said valve bore and inlet port whereby movement of said valve sealing land to open communication from said outlet or to said inlet port will result in a controlled directional injection of fluid under velocity directly into said inlet port, the transverse dimension of said valve bore (taken parallel to the axis of said rotor bore) being at least as great as the corresponding dimension of said intersecting inlet port, an oil reservoir and a passage from said reservoir to said inlet port providing a normal flow adjacent to and in the direction of said injection.

17. A pump comprising a pump housing, substantially parallel oppositely directed inlet and outlet ports communicating with said housing, fluid pumping means for moving fluid from said inlet port to said outlet port, a discharge passage communicating with said outlet port, a valve bore communicating with said inlet and outlet ports, a cylindrical spool valve having a sealing land axially movable to positions for opening or blocking said communication through said valve bore, an orifice interposed between said outlet port and said discharge passage for establishing a pressure differential therebetween increasing with flow through said discharge passage, means biasing said valve to close communication between said outlet and inlet ports, means ,responsive to said differential pressure urging said valve to open said communciation, a limited arc of intersection between said valve bore and inlet port whereby movement of said valve sealing land to open communication from said outlet or to said inlet port will result in a controlled directional injection of fluid under velocity directly into said inlet port, the transverse dimension of said valve bore (taken parallel to the axis of said rotor bore) being at least as great as the corresponding dimension of said intersecting inlet port, an oil reservoir and a passage from said reservoir to said inlet port providing a normal flow adjacent to and in the direction of said injection, said pump including a rotor passing through said inlet port and the direction of said injection being substantially tangential to and in the direction of said rotor travel.

18. A pump as set forth in claim 16 wherein an auxiliary passage is provided in said valve between said discharge passage and said pump inlet, and wherein safety release valve means is provided to normally block said auxiliary passage and to open said passage When a predetermined safety release pressure is established in sald discharge passage, said safety release valve means comprising a spring loaded ball valve normally blocking flow from said discharge passage through auxiliary passage.

19. A Ypump comprising a pump housing, a rotor bore in said housing, substantially parallel oppositely directed inlet and outlet ports communicating with said rotor bore, a valve bore intersecting said inlet and outlet ports, the

transverse dimension of said valve bore (taken parallel to the axis of said rotor bore) being atleast as great as the corresponding dimension of said intersecting inlet port, a` valve in said bore having a sealing land movable to admit uid injected under pressure from said outlet port directly into said inlet port in a direction substantially tangent to said rotor bore, a reservoir and a passage therefrom communicating with said inlet port, the flow from said reservoir being adjacent to and in the direction of said fluid injected under pressure.

20. A pump comprising a pump housing, a rotor bore Iin said housing, substantially parallel oppositely directed inlet and outlet ports in said housing communicating with opposite sides of said bore, a valve bore in said housing extending transversely of said rotor bore and intersecting said respective inlet and outlet ports, the transverse dimension of said valve bore (taken parallel to the axis of said rotor bore) being at least as great as the corresponding dimension of said intersecting inlet port, rotary pump means disposed in said rotor bore adapted to produce positive displacement pumping action between said inlet and outlet ports, and a valve movable to open or shut ol direct communication between said outlet and inlet ports through said valve bore, said valve and valve bore being constructed to open a limited discharge passage adapted to inject fluid under pressure in a direction substantially tangent to said rotor bore.

21. A pump comprising a pump housing, a rotor bore 'in said housing, inlet and outlet ports in said housing communicating tangentially with oppositesides of said bore, said ports being centrally disposed relative tothe length of said bore, a rotor eccentrically mounted in said bore extending beyond said inlet and outlet ports on either side, axially extending notches in the periphery of said rotor, loosely mounted slippers in said notches with resilient means urging them to engage the surface of said rotor bore and to move radially during passage of said inlet and outlet ports, the central portion of said slippers immediately adjacent the port areas in said housing being Y recessed to provide Wide open ow to and from the notch chambers under said slippers, a valve bore in said housing extending transversely of said rotor bore and intersecting said respective inlet and outlet ports, a fluid reservoir communicating with said inlet port, a spool valve axially movable to open or shut oi direct communication between said outlet and inlet `ports throughvr said valve bore, said valve having an annular land adapted to uncover a portion of said inlet port in said open position, said inlet port intersecting said valve bore over a limited arc such as to cause a coniined stream of output lluid under pressure to be injected from said valve bore directly into said inlet port substantially tangent Vto said rotor in the direction of slipper travel through said inlet port and in substantial alignment with said recessed central portion of said slippers when said valve land is moved to uncover said inlet port.

22. A pump comprising a pump housing, inlet and outlet ports communicating with said housing, uid pumping means for moving uid from said inlet port to said outlet port, a discharge passage communicating with said outlet port, a valve bore communicating with said inlet and outlet ports, a cylindrical spool valve having a sealing land axially movable to positions for opening or blocking said communication through said valve bore, an orifice interposed between said outlet port and said discharge passage for establishing a pressure differential therebetween increasing with iiow through said discharge passage, means biasing said valve to close communication between said outlet and inlet ports, means responsive to said differential pressure urging said valve to open said communication, a limited arc of communication between said valve bore and inlet port whereby movement of said valve sealing land to open communication from said outlet or to said inlet port will result in a controlled directional injection of uid under velocity directly into said inlet port, an oil reservoir `and a passage from said reservoir to said inlet port providing a normal ow adjacent to and in the direction of said injection, said pump including a rotor passing through said inlet port and the direction of said injection being substantially tangential to and in the direction of said rotor travel, an auxiliary passage being provided in said valve between said discharge passage and lsaid pump inlet, and safety release valve means being provided to normally block said auxiliary passage and to open said passage when a predetermined safety release pressure is established in said discharge passage.

23. A pump as set forth in claim 22 wherein said safety release valve means comprises a spring loaded cylindrical plunger normally blocking said auxiliary passage, an end area of said plunger being subjected to pressure in said discharge passage.

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Germany Oct. 30, 1933 

